Automated testing supports your constant effort in design and refactoring, and besides that ensures that your application actually works in a reliable and repeatable way. [...] In this article I'll describe the different categories of testing, as applied to a Zend Framework 1 application, but this classification pertains to every web application based on object-oriented programming. Since this kind of applications is obviously PHP-based, PHPUnit will be the tool of choice along with some of its standard extensions.
He looks at five different types of testing you can do on your application:
- Unit testing
- Pragmatic unit testing
- Functional testing
- Integration testing
- Acceptance testing
Not all of these can be done with PHPUnit on the backend, but they (mostly) have automated tools of their own like Selenium for frontend interface testing.